unit-test-standards

name	unit-test-standards
description	Python unit test standards including naming conventions (test__<what>__<expected>), behavioral testing patterns, coverage requirements (80% minimum), and tautological test detection. Use when reviewing tests, writing tests, or enforcing test quality. Trigger terms: unit test, test naming, test coverage, tautological test, behavioral test. Use when this capability is needed.

Python Unit Test Standards

Standards for writing meaningful, maintainable tests that verify behavior.

Test Naming Convention

# Unit tests: test__<what>__<expected>
def test__batch_allocation__reduces_available_quantity():
    pass

# Integration tests: test__<component>__<behavior>
def test__repository__saves_and_retrieves_batch():
    pass

# E2E tests: test__<use_case>__<scenario>
def test__order_allocation__happy_path():
    pass

Quality Criteria

Good (Behavioral)	Bad (Tautological)
Test outcomes and state changes	Assert mocked return values
Use real objects where possible	Test that assignment works
Verify domain invariants	Tests with no assertions
Test error conditions explicitly	Test implementation details

Coverage Requirements

Scope	Minimum	Target
New code	80%	90%
Critical paths	95%	100%
Overall project	70%	80%

File Organization

tests/
├── unit/           # Fast, isolated (<100ms each)
├── integration/    # Database, API, external services
├── e2e/           # Full workflow tests
└── conftest.py    # Shared fixtures

Tautological Test Detection

Tests that can't fail provide false confidence:

1. Mock assertion - Verifying mock returns what you told it to
2. Assignment test - Testing that x = 5 results in x == 5
3. Empty test - No assertions or only pass
4. Implementation test - Testing HOW not WHAT

See reference.md for detection patterns and examples.md for comparisons.

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